Driver circuits may be used in integrated circuits. For example, International Electrotechnical Commission (IEC) standard 61131-2 defines communications between sensors and activators and programmable logic controllers (PLC) in industrial applications. This standard allows both ends of the communications link between sensors and activators and PLCs to manage bus contention or driving high loads by defining a current limit in short circuit conditions. In such short circuit or overcurrent conditions, the driver circuits within the integrated circuits of either the sensors and activators or the PLCs would otherwise dissipate excessive current, exceeding safe operating temperatures and damaging the integrated circuits. Therefore, such driver circuits incorporate self-protection features to help ensure that safe operating temperatures are not exceeded, during short circuit conditions or otherwise.
Typically, such known self-protection features impose a fixed safe duty cycle on the output stage of the driver circuit during short circuit or overcurrent situations, with this fixed safe duty cycle being known to keep operating temperatures in a safe region. There may also be a fixed reduction of the value of the current limit in such conditions. While these self-protection features may be adequate to protect the integrated circuits from damage, they are inherently overly conservative to ensure they work in all conditions, meaning that average load current is lower than it could be. It would be desirable to be able to deliver a higher average load current than provided by driver circuits incorporating known self-protection features. Therefore, further development in this area is required.